Ecological Collapse from Sea Otter Overhunting

Trophic Cascade on the Pacific Coast

1. Sea Otter Decline: Hunted to near extinction for fur (18th–19th centuries).
2. Sea Urchin Explosion: Without otter predation, urchin populations surged.
3. Kelp Forest Destruction: Urchins overgrazed kelp holdfasts, turning lush forests into "urchin barrens."
4. Ecosystem Ripple Effects: Loss of kelp habitat reduced fish, invertebrates, and marine mammals; coastal erosion increased.
5. Fishery Impacts: Commercial species dependent on kelp nurseries declined.

Reintroduction of sea otters in some areas has triggered recovery, demonstrating their role as a keystone species.